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McIntosh Power Amplifier MC303, Service Manual

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McIntosh Power Amplifier MC303 Service Manual Download Page 36

The continuous improvement of its products is the policy of McIntosh Laboratory Incorporated, who reserve the right to improve design without notice. Because 

of the constant upgrading of McIntosh products’ circuitry and components, the Company cannot insure, and does not warrant, the accuracy of the within schematic 

material, which is intended for information only.

McINTOSH LABORATORY, INC.,      2 CHAMBERS STREET,    BINGHAMTON,   NEW YORK   13903    Printed in U.S.A.    Part Number 041173

SERIAL NO. ZH1001 And Above

MC303

POWER AMPLIFIER

Summary of Contents for Power Amplifier MC303

Page 1: ...uppy Schematic and PCB 9 12 Control Schematic and PCB 13 16 Input Channel 1 2 Schematic and PCB 17 20 Input Channel 3 Schematic and PCB 21 24 Capacitor Schematic and PCB 25 28 Heatsink Schematic and PCB 29 34 Terminal Schematic and PCB 35 38 Display Schematic and PCB 39 44 Meter Control Schematic and PCB 45 46 Meter Light Schematic and PCB 47 48 Parts List 51 55 Repacking Instruction 57 CONTENTS ...

Page 2: ...8dB Frequency Response 0 0 25dB from 20Hz to 20 000Hz 0 3dB from 10Hz to 100 000Hz Input Sensitivity for rated output 1 7 Volt Unbalanced 3 4 Volt Balanced Signal To Noise Ratio A Weighted 112dB below rated output Intermodulation Distortion 0 005 maximum if the instantaneous peak power output does not exceed twice the rated power output for any com bination of frequencies from 20Hz to 20 000Hz Wid...

Page 3: ...MC303 REAR PANEL 3 ...

Page 4: ...4 SECTION LOCATIONS ...

Page 5: ...MC303 BLOCK DIAGRAM 5 ...

Page 6: ...6 NOTES ...

Page 7: ...8 J9 J4 J3 J6 J5 J1 J2 BLK WHT BLK F1 J5 J4 J6 BLU GRN BLU T4 C1 RED RED D1 J4 J5 RED GRN J6 YEL J7 1 2 75V 75V J3 75V 75V J2 75V 75V J1 75V 75V 1 2 75V 75V J5 1 2 75V 75V J5 J8 1 J9 5 1 J3 15V 15V 6 MUTE MET THRM PG 1 J2 8 Ohm 4 2 Ohm 1 J1 4 15V 15V AMP GND J6 J7 J4 VIO WHT 1 15V 15V 6 MUTE MET THRM PG 8 Ohm 2 Ohm 15V 15V AMP GND J6 J7 J4 VIO WHT 1 J7 4 15V 15V AMP GND 1 J6 4 AMP GND 1 J6 4 8 Ohm...

Page 8: ... PRIMARY 240V 220V 120V 2 6 8 4 1 3 5 7 PRIMARY T1 3 1 4 2 K1 100V t RT1 t RT2 J7 1 3300pF C1 J6 1 J16 1 J16 2 RLY TP TEST ONLY NO CONNECTION 2 1 3 IN OUT U1 47uF C3 3A t R1 3300uF C2 PGND 1 ORN J21 9 PWR RLY 1 ORN J22 1 82k R2 3 1 2 Q1 PWR TRANSFORMER THERMAL SWITCH J23 11 9 5VBU GND 9 J23 1 J23 2 TO DISPLAY FROM DISPLAY J23 12 J23 3 J23 4 J23 5 J23 6 J23 7 J23 8 J23 9 J23 10 D4 D5 D2 D3 F1 0V J4...

Page 9: ...POWER AMPLIFIER MC303 11 12 2 BACKUP POWER SUPPLY 750975 PCB ...

Page 10: ...k R25 POWER 4 75k R30 3 1 2 Q12 15V 2 21k R28 1uF C14 47 5k R22 24V 5 PC OUT TO CH3 INPUT FROM CH3 INPUT 1 1 1 BLU GRN BLU 1 1A t R4 047uF C1 3 1 2 IN OUT U4 3300uF C4 2 3 1 IN OUT U3 1uF C9 100uF C7 1uF C10 3300uF C5 100uF C6 D2 D3 D1 D4 15V 15V J4 J5 J6 1 1A t R5 1 2 HS1 1 2 HS2 PWR TRANSFORMER SECONDARY 100k R7 24V 1 2 3 7 B GND 14 U1 1 12 13 11 U1 4 22 1k R8 47 5k R9 5VBU METER LIGHT CONTROL 5...

Page 11: ...POWER AMPLIFIER MC303 15 16 3 CONTROL 750886 PCB ...

Page 12: ... 221k R7 221k R6 10k R5 20K R3 20K R4 7B 7B GND 10uF C10 47pF C12 47pF C11 CH2 BAL TO UNBAL AMP AM P 2 TO CH2 HTSNK 10uF C9 10k R15 2 3 1 8 4 B B U1 1 47pF C13 10k R16 221k R14 221k R13 CH2 INPUTS 4 2 3 1 S G J4 1 2 J5 10k R12 20 K R10 20K R11 10uF C1 1uF C2 1uF C3 10 R1 10 R2 1uF C14 1uF C15 7A 7A CH2 HTSNK FRO M 2 21 R18 2 21 R17 2 21 R19 2 21 R20 J7 1 J7 2 J7 3 J7 4 J6 3 J6 4 GP1 0V 0V 0V 0V 0V...

Page 13: ...POWER AMPLIFIER MC303 19 20 4 INPUT CH 1 2 750866 PCB ...

Page 14: ... 3 1 8 4 B B U1 1 47pF C9 10k R9 15V2 15V2 221k R6 221k R7 CH3 INPUTS 4 2 3 1 S G J3 1 2 J4 10k R5 20K R3 20K R4 6 5 7 U1 2 100 R10 1 3 2 J5 1 4 6 5 J5 2 POWER CONTROL IN OUT 3 3 TO CONTROL 3 10uF C1 1uF C2 1uF C3 10 R1 10 R2 PC MET PC IN PC OUT 1uF C4 15V2 7C 7C CH3 HTSNK FROM 2 21 R11 2 21 R12 GND 3 J1 1 J1 2 J1 3 J1 4 GP1 J2 1 J2 2 J2 3 J2 4 J2 5 0V 0V 0V ...

Page 15: ...POWER AMPLIFIER MC303 23 24 5 INPUT CH 3 750887 PCB ...

Page 16: ... J3 1 J3 2 J6 J4 J7 TO CH1 HTSNK 75V 75V 7A 7A 1 1 1 1 RED GRN YEL BLK TO CH2 HTSNK 75V 75V 7B 7B TO CH3 HTSNK 75V 75V 7C 7C J2 1 J2 2 27000uF C1 27000uF C3 27000uF C2 27000uF C4 PWR TRANSFORMER SECONDARY RED RED YEL 0 22uF BRIDGE RECTIFIER T4 ...

Page 17: ...POWER AMPLIFIER MC303 27 28 6 CAPACITOR 750986 PCB ...

Page 18: ...C5 100 R3 100 R2 3 1 2 Q4 2 1 3 Q10 2 1 3 Q12 3 2 1 Q18 3 32k R35 3 2 1 Q7 806 R30 267k R38 3 2 1 Q9 3 2 1 Q11 0V 0V 0V 8 4 B B U1 1 B B B B 14V 14V 14V 14V 8 OHM FB 2 OHM FB 22uF C13 475 R25 4 75k R22 220uF C9 475 R10 15V 9 1pF C14 DRV DRV TO DISPLAY THERM 9 470 3 1 2 o t RT1 OUTPUT METER 4 5 4 5 AM P GND FROM INPUT PG PG 9 METER METER 10uF C16 47 5 W R29 75V B 47 5W R28 10uF C15 75V B MUTE 9 3 3...

Page 19: ... 8k R53 1 8V 2 1 Q21 3 2 1 Q26 1 3 2 1 Q33 1 T O A U T O F R M R 5 4 Q34 2 1 5k R51 3 2 1 Q28 1 3 2 1 Q31 1 J6 100pF C26 5 4 Q33 2 1 8k R50 500 2 3 1 CCW R52 3 2 1 Q32 1 3 2 1 Q27 1 OUTPUTS DRIVER DRIVER OUTPUTS 5 4 Q31 2 5 4 Q32 2 47x2 2 1 3 R55 3 1 2 Q37 1uF C29 3 2 1 Q36 1 3 2 1 Q35 1 5 4 Q35 2 5 4 Q36 2 5 4 Q30 2 5 4 Q29 2 5 4 Q28 2 5 4 Q27 2 5 4 Q26 2 5 4 Q25 2 47x2 2 1 3 R61 J7 1 WHT VIO 47x...

Page 20: ...33 34 7 HEATSINK 750868 750881 PCB 129944 ...

Page 21: ...POWER AMPLIFIER MC303 35 36 8 TERMINAL 750890 SCH J1 J3 J2 J4 1 1 1 1 ORN RED BLU BLK FROM AUTOFORMER BP4 BP3 BP2 BP1 J5 J6 1 J6 4 7 7 TO HEATSINK 1 8 4 2 COM ...

Page 22: ...37 38 8 TERMINAL 750890 PCB ...

Page 23: ...7A 7A 7A 7B 7B 7B 7C 7C 7C J6 4 5VBU 2 5VBU J6 1 J6 12 2 GND 2 PW R RLY T O B A C K U P F R O M B A C K U P J8 7 J8 5 J8 4 J8 18 3 3 2 k R 6 681 R7 3 1 2 Q5 CH1 POWER GUARD 4L 3 3 2 k R 4 681 R5 3 1 2 Q4 CH2 POWER GUARD 3 3 2 k R 2 681 R3 3 1 2 Q3 CH3 POWER GUARD J8 16 J8 13 J8 12 J8 15 J8 17 J8 14 J8 10 J8 2 3 3 2 k R 1 0 3 1 2 Q7 1 2 1 k R 1 1 3 1 2 Q6 2 2 1 k R 2 0 THERMAL PROTECTION 332 R8 1 2...

Page 24: ... C12 221 R47 10uF C6 150k R39 CH3 METER DRIVER D15 7 5 6 U1 2 3 1 2 Q13 3 1 2 Q19 14V 14V 475k R50 D9 14V 1 3 2 4 11 B B U1 1 20K R42 2 21k R53 1 1 T O C H 3 M E T E R 100k CCW 1 2 3 R59 J15 1 J15 2 CH2 METER LOG AM P CH3 M ETER LOG AM P 8 10 9 U1 3 14 12 13 U1 4 CH1 M ETER CAL CH2 METER CAL CH3 M ETER CAL 1uF C3 20K R31 4 99k R32 15V 3V 3V 3V 3V 3V 3V 3V 3V 3V 3V 3V 10uF C1 15V 1 2 3 S G D Q20 MU...

Page 25: ...POWER AMPLIFIER MC303 43 44 9 DISPLAY 750869 PCB ...

Page 26: ...1 500 1 2 3 CCW R2 6 500 1 2 3 CCW R2 5 200 CCW 1 2 3 R30 500 1 2 3 CCW R2 4 T O C H 1 M E T L IG H T T O C H 2 M E T L IG H T T O C H 3 M E T L IG H T COLOR INTENSITY COLOR INTENSITY COLOR INTENSITY GND 11B 11B 11B GND 11C 11C 11C GND J9 3 J9 7 J9 2 DS 2 DS 3 DS 4 J9 4 J9 6 J9 1 J9 5 J9 17 J9 9 J9 12 J9 14 J9 15 9 9 9 9 9 9 9 9 9 9 9 9 GND GND GND MT1 LT MT2 LT MT3 LT PG3 LT PG2 LT PG1 LT PG COM ...

Page 27: ... 6V 5 6V BLU GRN 5 6V 2 1 3 4 R B G D1 2 1 3 4 R B G D2 2 1 3 4 R B G D6 J1 1 J1 2 J1 3 J1 4 J1 5 J1 6 J1 7 J1 8 J1 9 J1 10 J1 11 J1 12 2 1 3 4 R B G D5 2 1 3 4 R B G D3 2 1 3 4 R B G D4 221 R2 221 R4 221 R6 221 R8 221 R10 221 R12 681 R1 681 R5 681 R9 681 R3 681 R7 681 R11 10 10 10 10 10 10 10 10 10 10 10 10 47 48 ...

Page 28: ...49 50 NOTES ...

Page 29: ...MONO 1UF 50V 20 Z5U 061346 C14 CAP MONO 1UF 50V 20 Z5U 061346 D1 DIODE RECTIFIER 070175 D2 DIODE RECTIFIER 070175 D3 DIODE RECTIFIER 070175 D4 DIODE RECTIFIER 070175 HS1 HEATSINK TO 220 080021 HS2 HEATSINK TO 220 080021 INSULATOR ISOSTRATE TO 220 084133 J4 BLADE FASTON W FEET 117708 J5 BLADE FASTON W FEET 117708 J6 BLADE FASTON W FEET 117708 J8 CONN 18 PIN FFC 117908 J9 CONN MALE 5 PIN 0 1 POST AS...

Page 30: ...ES FP 10 OHM 5 1 4W 137105 R3 RES MF 20K 1 1 4W 144524 R4 RES MF 20K 1 1 4W 144524 R5 RES MF 10K 1 1 4W 144504 R6 RES MF 221K 1 1 4W 144629 R7 RES MF 221K 1 1 4W 144629 R8 RES MF 10K 1 1 4W 144504 R9 RES MF 10K 1 1 4W 144504 R10 RES MF 20K 1 1 4W 144524 R11 RES MF 20K 1 1 4W 144524 R12 RES MF 10K 1 1 4W 144504 R13 RES MF 221K 1 1 4W 144629 R14 RES MF 221K 1 1 4W 144629 R15 RES MF 10K 1 1 4W 144504...

Page 31: ...MF 4 99K 1 1 4W 144521 R9 RES MF 10K 1 1 4W 144504 R10 RES MF 475 OHM 1 1 4W 144509 R11 RES MF 10K 1 1 4W 144504 R12 RES MF 40 2K 1 1 4W 144525 R13 RES MF 267K 1 1 4W 144532 R14 RES MF 267K 1 1 4W 144532 R15 RES MF 499 OHM 1 1 4W 144510 R16 RES MF 365 OHM 1 1 4W 144505 R17 RES MF 20K 1 1 4W 144524 R18 RES MF 200K 1 1 4W 144531 R19 RES MF 475 OHM 1 1 4W 144509 R20 RES MF 6 49K 5 1 4W 144617 R21 RES...

Page 32: ...J5 CONN 18 PIN FFC 117908 J6 CONN 12 PIN FFC 117907 J7 CONN 3 POS MALE MTS100 NORMAL 117214 J8 CONN 18 PIN FFC 117908 J9 CONN 18 PIN FFC 117908 J10 CONN 12 PIN FFC 117907 J11 CONN 12 PIN FFC 117907 J12 CONN 12 PIN FFC 117907 J13 HEADER 2 PIN LATCHING 117766 J14 HEADER 2 PIN LATCHING 117766 J15 HEADER 2 PIN LATCHING 117766 PCB1 PC BD DISPLAY 129914 Q1 TRANSISTOR PNP SILICON 132304 Q2 TRANSISTOR NPN...

Page 33: ...W 144579 R19 RES MF 12 1K 1 1 4W 144550 R20 RES MF 2 21K 1 1 4W 144584 R21 RES MF 4 75K 1 1 4W 144520 R22 RES MF 1 5K 1 1 4W 144539 R23 RES MF 806 OHM 1 1 4W 144512 R24 POT TRIM 500 OHM 10 HORIZ ADJ 134508 R25 POT TRIM 500 OHM 10 HORIZ ADJ 134508 R26 POT TRIM 500 OHM 10 HORIZ ADJ 134508 R27 RES MF 1K 1 1 4W 144513 R28 POT TRIM 200 OHM 20 HORIZ AD 134506 R29 POT TRIM 200 OHM 20 HORIZ AD 134506 R30 ...

Page 34: ...56 NOTES ...

Page 35: ...sure the proper equipment location on the bottom pad Failure to do this will result in shipping damage Use the original shipping carton and interior parts only if they are all in good serviceable con dition If a shipping carton or any of the interior part s are needed please call or write Customer Service Department of McIntosh Laboratory Refer to page 3 Please see the Part List for the correct pa...

Page 36: ... of the constant upgrading of McIntosh products circuitry and components the Company cannot insure and does not warrant the accuracy of the within schematic material which is intended for information only McINTOSH LABORATORY INC 2 CHAMBERS STREET BINGHAMTON NEW YORK 13903 Printed in U S A Part Number 041173 SERIAL NO ZH1001 And Above MC303 POWER AMPLIFIER ...

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